CHAPTER XVII PRIMATES Order XIII. THE highest of mammals, the Primates,1 may be thus differ- entiated from other groups :—Completely hairy, generally arboreal mammals, with fire digits on fore- and hind-limbs, provided with flat nails (except in the case of certain Lemurs and the Marmosets), the phalanges that Lear these "being flattened at the extremity and expanded rather than diminished in size. The fore-feet are grasp- ing hands as a rule, and the hind-feet walking as well as (generally) grasping organs, and the mode of progression is plantigrade. The teats, except in Ohiromys, are thoracic, and even axillary in position. The skull is characterised By the fact that the orbital and the temporal vacuities are, at least partly, separated by bone. The clavicles are always present. The carpus lias separate lunar and scaphoid bones, and the centrale is often present. There is rarely an entepicondylar foramen in the humerus, except in some archaic Lemurs. The femur has no third trochanter. The stomach is usually simple, being saeculated only in Senmopithecinae. The caecum is always present, and often large. This great group could be easily divided into two separate orders, the Apes and the Lemurs, if it were not for certain fossil types. As will be seen from the description of Nesopithecus and of Tarsius, the actual hard and fast lines between all Apes and all Lemurs are very few. On the other hand, it is a little difficult to draw a hard and fast line between the Primates as a whole—or at least between the Lemurine section—and the Creodonta, a 1 For a general account of the Primates, see Forbes In Mien's Library, London, 1894.